1. Field of the Invention
This invention relates to a probing test machine for testing the electrical characteristics of semiconductor wafers, liquid crystal display elements, printed circuit boards and so forth and more particularly to an electric probing test machine constructed such that the loading/unloading unit can be separated from the test stage unit.
2. Description of the Related Art
Semiconductor devices such as ICc and LSIs, LCD elements and printed circuit boards are subjected to several tests in the manufacturing process to evaluate their electrical characteristics.
As an example, in a wafer test in which continuity is tested on a circuit of a device pattern formed on a semiconductor wafer, the probes of a wafer probing machine are brought into contact with the electrodes of the device pattern and a high frequency current is passed through the probes to the circuit to measure the electrical characteristics of that device pattern.
Wafer probing machines used for wafer testing are illustrated in Japanese Utility Model Disclosure No. 85-41045 and Japanese Patent Disclosure No. 86-168236. These machines are of the so-called one-loader, one-stage type which has one test stage unit for one loading/unloading unit.
Japanese Patent Disclosure No. 86-168236 also discloses the so-called one-loader, multi-stage type wafer probing machine in which one loading/unloading unit is used commonly for a plurality of test stage units.
In those wafer probing machines, the test stage unit is used to test the electrical characteristics of a semiconductor wafer on the test stage and the loading/unloading unit transfers semiconductor wafers between a wafer cassette and the test stage.
A large number of wires are installed in both the test stage unit and the loading/unloading unit. Therefore, maintaining those units, which includes changing the wiring, takes a long time. In order to reduce maintenance time, those units are constructed as independent components, thereby making maintenance work easier.
Meanwhile, in a conventional one-loader, multistage type wafer probing machine, for example a one-loader two-stage type machine, there are two loading/unloading units on the lateral sides of the test stage unit. Therefore, the working space is very small and it is difficult and time-consuming to maintain the test stage unit and the loading/unloading unit.
In adjusting the internal mechanism of the loading/unloading unit for example, the working space is limited to the front side of the loading/unloading unit. Therefore, when the part to be maintained is positioned at the lateral side of the test stage unit, the operator cannot reach that part since the loading/unloading unit is in his way.
Also with a one-loader, one-stage type probing machine, in maintaining the test stage unit, the working space for maintenance is significantly limited by the loading/unloading unit. This makes it difficult to adjust the mechanisms at the mutually adjoining faces of the test stage unit and the loading/unloading unit.